Ported and 4th Order Bandpass compatible
I show a quick, easy though expensive method for finding port tuning frequency, then an inexpensive/more complex method which is equally reliable.

Timestamps:
0:00 Introduction
0:24 Quick Method
1:56 Cheap Method
6:26 Measured results
9:04 Calculating Resistances for each frequency
10:46 Graphing Impedance Curve
13:23 Finding tuning frequency
14:48 Conclusion

Frequencies used:
16Hz
20Hz
25Hz
28Hz
32Hz
36Hz
40Hz
50Hz
60Hz
72Hz

Dayton Audio DATS V3:
https://www.parts-express.com/dayton-...

Required for Cheap test-
Audio source with clean test tones
Amplifier
Multimeter capable of measuring AC voltage (most digital)
1 Ohm resistor (several watt suggested)
Alligator leads may come in handy to connect components
Pen/Pencil
Paper
Calculator
Clamp meters can be inaccurate for low currents, so I'd suggest measuring voltage across the 1 Ohm resistor.